diff --git a/distributed/worker_state_machine.py b/distributed/worker_state_machine.py
index 2848f4cd41b..da4fc206cf7 100644
--- a/distributed/worker_state_machine.py
+++ b/distributed/worker_state_machine.py
@@ -43,34 +43,32 @@
 logger = logging.getLogger("distributed.worker.state_machine")
 
 if TYPE_CHECKING:
-    # TODO import from typing (requires Python >=3.10)
-    from typing_extensions import TypeAlias
+    # TODO import from typing (TypeAlias requires Python >=3.10)
+    # TODO import from typing (NotRequired requires Python >=3.11)
+    from typing_extensions import NotRequired, TypeAlias
 
     # Circular imports
     from distributed.diagnostics.plugin import WorkerPlugin
     from distributed.worker import Worker
 
-    # TODO move out of TYPE_CHECKING (requires Python >=3.10)
-    # Not to be confused with distributed.scheduler.TaskStateState
-    TaskStateState: TypeAlias = Literal[
-        "cancelled",
-        "constrained",
-        "error",
-        "executing",
-        "fetch",
-        "flight",
-        "forgotten",
-        "long-running",
-        "memory",
-        "missing",
-        "ready",
-        "released",
-        "rescheduled",
-        "resumed",
-        "waiting",
-    ]
-else:
-    TaskStateState = str
+# Not to be confused with distributed.scheduler.TaskStateState
+TaskStateState: TypeAlias = Literal[
+    "cancelled",
+    "constrained",
+    "error",
+    "executing",
+    "fetch",
+    "flight",
+    "forgotten",
+    "long-running",
+    "memory",
+    "missing",
+    "ready",
+    "released",
+    "rescheduled",
+    "resumed",
+    "waiting",
+]
 
 # TaskState.state subsets
 PROCESSING: set[TaskStateState] = {
@@ -112,14 +110,11 @@ class SerializedTask(NamedTuple):
     task: object = NO_VALUE
 
 
-class _StartStopRequired(TypedDict):
+class StartStop(TypedDict):
     action: Literal["compute", "transfer", "disk-read", "disk-write", "deserialize"]
     start: float
     stop: float
-
-
-class StartStop(_StartStopRequired, total=False):
-    source: str
+    source: NotRequired[str]
 
 
 class InvalidTransition(Exception):
@@ -1029,18 +1024,12 @@ class SecedeEvent(StateMachineEvent):
     compute_duration: float
 
 
-if TYPE_CHECKING:
-    # TODO remove quotes (requires Python >=3.9)
-    # TODO get out of TYPE_CHECKING (requires Python >=3.10)
-    # {TaskState -> finish: TaskStateState | (finish: TaskStateState, transition *args)}
-    # Not to be confused with distributed.scheduler.Recs
-    Recs: TypeAlias = "dict[TaskState, TaskStateState | tuple]"
-    Instructions: TypeAlias = "list[Instruction]"
-    RecsInstrs: TypeAlias = "tuple[Recs, Instructions]"
-else:
-    Recs = dict
-    Instructions = list
-    RecsInstrs = tuple
+# TODO remove quotes (requires Python >=3.9)
+# {TaskState -> finish: TaskStateState | (finish: TaskStateState, transition *args)}
+# Not to be confused with distributed.scheduler.Recs
+Recs: TypeAlias = "dict[TaskState, TaskStateState | tuple]"
+Instructions: TypeAlias = "list[Instruction]"
+RecsInstrs: TypeAlias = "tuple[Recs, Instructions]"
 
 
 def merge_recs_instructions(*args: RecsInstrs) -> RecsInstrs: